Rocket motors



Feb. 28, 1961 F. J. PORCHER ROCKET MOTORS Filed Feb. 11, 1959 1 m 4 M WM\w SMWWW .mP A w mm; Na d w a m Y flu 8 mm o 0N 7 *3 A .NN a a X y $12@535 F.J. PORCHER ROCKET MOTORS Feb. 28, 1961 Filed Feb. 11, 1959IIIIIIIIII 7;;! IW

FIG. 2.

2 Sheets-Sheet 2.

INVENTOR:

Fr eder/c/r Jar es Pore/rel,

ATTORNEY$..

United States i MoTofiS Freaerick-James-Parehr;Eagaaston;niigmaagasstgnei Imperial Chemical Industries Limited, Isond'on, Eng:-

land, acbrpor'atiom of Great Britain- Firearb. 1i, 19'ss;s'"er.1 to:1922:? Claims priority; appticanon Great-Kirstin New-25,: 1958'- 4Claims. (e1; 66 45.6

invention is c'cincer'ned era rocket meters of the" kind in which solidpropellan is This application is a" continua on-in-part'-'of-"my*afi-*plication Serial No; 641,423, filcd'Feb: 20 1957 now abandoned; v p

Long-burning rocEetniot'c'Srsemploy either-a s'lbw' burrring propellantburningradially-oi a relatively f "tb' ri-- in'g propellant burningcigarette-Wise; Limitations ma dial dimensions and difiicul t yofproducing" rcpeuants having a burning rate suitable for the dimensionwas burning-time factors militate ags'instthe" fadial bu configuration:on theother nan narg'ec changes occurring during warning of the "sconfiguration are objectionablei I posed to overcome the"- latter discigarette-burning configuration 1n whieh sing burns fro'rn-botliendssimultaneously p at the head-end of are reaper ng via int axiallylo'eatetl' transfer tune-'- to the n' iidot 5 motor. B u't'hereagaimother disadvzifit iri ff" the transrerfiib whieh: transfer headendto the? e-end-"of of material whie is not onl'y" capable of resistingthe erosive action of the h t gas flow. Those materials which aresufliciently heat -ahd erosibn resi's tant difficlllf" f6 b'bnd to; thecharge and also" their respe'cti e coeffibifi O f-e ans h aredilfere'nti The l tffctf issi'gn-ificanf-b motors have: td'betemperafnre'wydd several 1 temperatures ranging" ans-matey fromarctic-to" tropi a1 conditions,- and in th'e' course omens test nthecharge frequently separates from lie-transfer t'u the'result that thecharge is" liable to beigliitdfiiiiifith tio'n'ally at a surface'other'than anend face 'Acc'ording' to-the'present invention, Meekermotor comprises a solid propellant eliarg eflsecur'ed creme: torcasingand" a second-so 'd i d in. the casing" in such mariner as to preA flow" ofpro'p'ellant over are outer" suifafc 0nd charge betweesaidsurfaceand thecasingj said'sec on'd charge beingjspac'e'djfrom thefirst-mentionedc h'ar "a towards the rear'end'of the niotor'whereby"the' adjacent endlsurfaces ofthetwo charges are spacedapart eachother,said adjacent endfsurfacesbe'ingfsilrfaces'f at which thehargsstsurnwhen ignited; ije. ignition ena surfaces, each charge having"that" part of its-surraeee'e posed to the except th ghi'tioncndsurf ce,c6vere by ignition-preventing means; for

Patented Feb. 28, 1 9.61

which pressurises' the end of the charge opposite to it's ignitionend issubstantially static gas, the flow path for thesecond charge being. byway of a clearance between the'transfer tube and wall of said passage,the transfer tube and motor casing'being connected rearwardly of thesecond charge by a gas-tight joint.

In one embodiment of the invention, two propellant charges are employedin axial alignment within the motor casing, and are spaced apart. 1 Inpart of the space between adjacent ends of the two charges (which arethe ignition end surfaces) there is disposed an ignition means whichwhen fired ignites substantially simultaneously both the ignition end"surfaces. The second or rear charge has a bore through which extends agas transfer tube, the said tube serving to convey all the hot gases"from both charges to the atmosphere external to the rocketthrough anaperture in the rear end wall of thecasing". The two charges are;secured to" the end walls of thecasing at their respective forward andrearw'ardends and-the securing means thus remain operaavesubstantiallythroughout the burning period. Moreover; the'transfertube-is secured to the wall of the aper tureiri a gas-tight manner,and'isthe sole exit for the hot area so that all the gases frombothportions' of the chargef'afe caused to now through thefe'r tirelength off thetube'and escape therefromo'nly via the motor nozzle;

The second charge is supported" against differential as-pressure theendsof the charge by reason of the fact that some propellant gas initiallyflows through the clearance between the transfer tube and charge into aspace behind'the charge where it remains as substan ti'ally static gasin contact with the rear end'thereof.

The forwardcharge may be supportedagainstdiifer entialgaspr'essure inthe same way, ize. by the use of a transfer tube-to duct the propellantgasto the end of the ch'argeremote'f ror'n' its ignitionend; Preferably,however the forward charge is solid throughout and the pro-'pella'ntgas-flow to support it is through an annular clear auce betweenthe outer surface of the charge" and the inner surface of-the motorcasing. To enable the gas 'to have access to the forward end of thischarge the means supporting. the charge in the casing is provided with apassageway to let the gas through.

A racket motor in accordance with the invention has several advantagesover hitherto proposed rocket motors. For example, bonding of the chargeto the transfer tube and the difficulty of ensuring that the bondremains good after the temperature cycle test are avoided. Moreover,

since all the hot gases must pass through the transfer tube, and thereisno continuous flow of hot gases through the space betw'eenthechargeandthe casing or the space between thecharge andthe -transfer tube,the"normal"in'-' Figure 2 is a similar section of the nozzle end of themotor.

The nozzle is connected to the transfer tube shown in Figure 1 eitherdirectly or by means of an extension of the transfer tube or by aseparate blast tube (not shown).

Referring now to Figure l, the numeral 1 indicates a cylindrical motorcasing having forward and rear end closures Z, 3 secured thereto byscrews 4. Disposed with-- inthe casing 1 at the forward end is a firstpropellant charge 5 and spaced therefrom in the axial direction towardsthe rear end of the casing 1 is a second charge 6, the remote ends ofthe two charges being spaced from their respective end closures asshown. The adjacent surfaces 7, 8 of the two charges 5 and 6 are theignition end'surfaces and each charge is covered on all of its sur faceother than the ignition end surface with ignitioninhibiting materialsuch as cellulose acetate.

Referring now to the first charge, the inhibiting material takes theform of layers 9 and 10 and a ferrule portion 11. The ferrule 11 isprovided with an annular groove 12 and the charge 5 is supported inposition by means of a grain hold-back ring 13 screwed to the endclosure 2, the grain hold-back ring 13 having a claw portion 14 whichengages in the groove 12 in the ferrule 11.,

A shock-absorbing ring 15 is located in the groove 12 and provides agas-tight joint between the claw portion 14 and the ferrule 11.

The grain hold-back ring 13 is designed to leave a clearance 16 betweenitself and the ferrule 11 and is provided with a number ofcircumferentially spaced holes 17. As shown, there is a small gap 18between the outer surface of the charge 5 and the inner surface of thecasing .l and the arrangement thus provides a flow path for propellantgas from the space between the charges, along the annular gap 18,through the holes 17 and clearance 16 and into the space 19 between theforward end face of the charge 5 and the end closure 2. The end closure2 is plugged at 20 and the space 1% therefore provides a dead end forthe gas flow.

The second charge 6 is also provided with layers of inhibiting materialand a ferrule of inhibiting material, the

reference numerals for these parts being those employed for thecorresponding parts of the first charge 5. The charge 6 is secured inposition in a similar manner to the charge 5 by means of a grainhold-back ring 21, the grain hold-back ring 21 differing from the ring13 for the charge j 5 in that it has no holes corresponding to the holes-17 A gas-tight seal 22 is interposed between the ring 21 and endclosure 3 and it will thus be seen that the charge 6 is supported at itsouter surface in a manner which will prevent continuous flow of gasalong the gap between through the leads 29 to cause ignition of thecharges 5 and 6 on the ignition end surfaces 7 and 8. The igniting means28 soon burns away and disintegrates leaving the forward end of thetransfer tube 23 open for the admission thereto of propellant gasgenerated in the space between the two charges. When the charges startto burn there is an initial flow of propellant gas along the annular gap18 between the charge 5 and the casing, through the flow path describedabove and into the space 19. Similarly there is an initial gas flow intothe space 27 behind the charge a but in this case the flow path is byway of the clearance Both charges are thereby supported at their endsremote from the ignition ends by means of substantially static gas whichhas negligible erosive effect on the ignition-inhibiting material.

The main bulk of the gas generated is conveyed through the transfer tube23 towards the nozzle 30 and the position of the forward end of thetransfer tube 23 is such that no erosion of the ignition-preventingmaterial 24 in the passage in the charge 6 occurs.

As the charges continue to burn, the burning surfaces recede from oneanother maintaining the centre of gravity of the system in a practicallyconstant position. Since "reference to the drawing of a rocket motorcontaining only two charges of propellant material. It will beappreciated, however, that the invention may be employed with three ormore charges of propellant material. In

such arrangements any number of charges may be placed in the motor usingthe construction and arrangement described above for the second charge.That is to say the charges will be traversed through by transfer tubesand will be pressurised at the ends opposite to their ignition ends bymeans of static gas in the manner aforementioned.

In f'this case some of the transfer tubes will be fixed to some internalbulkhead and will not be connected directly to the nozzle but will beused to transfer gas from one chamber to another in the motor.

that the charges will be arranged in accordance with the 6 in thepassage is covered with ignition-preventing ma-- terial 24 and thereexists a clearance 25 between this material 24 and the transfer tube 23.

the end closure 3 and is fitted in the end closure 3 in a The transfertube 23 passes out of the casing through 1 maximum acceptable centre ofgravity change during burning for the motor as a whole, the dispositionof the ignition ends of the charges being such that gas flows into atransfer tube without eroding the surface of its adjacent charges.

has a reduced cross-section at one or more positions along its length.

I claim:

1. A rocket motor comprising a casing, first and second propellantcharges mounted in said casing in spaced apart relationship, a gas tightjoint between said second charge and said casing whereby. passage of gasover the outer circumferential surface of said second charge isprevented, the facing surfaces of said propellant charges "constitutingignition end surfaces and the other surfaces of said charges beingcovered with ignition-inhibiting macasing, a gas tight joint betweensaid transfer tube and v said casing, said passage being larger thansaid gas trans tween the charge 6 and end closure 3 is a dead-end forfer tube whereby gases generated in the space between said charges mayflow between said gas transfer tube and said second charge to the remoteend of said second charge to provide a cushion of substantially staticgas to remote end of said first charge to provide a cushion ofsubstantially static gas to equalize the pressure on said first charge,and means for igniting the ignition end surfaces of said chargessubstantially simultaneouslyr It will be understood The employment ofmore than two charges is sometimes dictated by the need to using acasing which I 2. A rocket motor as defined in claim 1, wherein saidfirst propellant charge is located at the head end of the motor and issolid throughout, and the flow path for said first charge is by way of agap between the charge and the casing and through a passage provided inthe means by which said charge is mounted in the casing..

3. A rocket motor comprising a casing, first and second propellantcharges mounted in said casing in spaced apart relationship, the facingsurfaces of said propellant charges constituting ignition end surfacesand the other surfaces of said charges being covered withignition-inhibiting material, a passage through said second charge, anda gas transfer tube extending through said passage, said passage beinglarger than said gas transfer tube whereby gases generated in the spacebetween said charges may flow between said gas transfer tube and saidsecond charge to the remote end of said second charge to provide acushion of substantially static gas to equalize the pressure on saidsecond charge.

remote end of said first charge to provide a cushion of substantiallystatic gas to equalize the pressure on said first charge.-

References Cited in the file of this patent UNITED STATES PATENTS2,206,809 Denoix July 2, 1940 2,816,721 Taylor Dec. 17, 1957 FOREIGNPATENTS 10,008 Great Britain Ian. 11, 1844

